I’m looking for a simple encryption tutorial, for encoding a string into another string. I’m looking for it in general mathematical terms or psuedocode; we’re doing it in a scripting language that doesn’t have access to libraries.
We have a Micros POS ( point of sale ) system and we want to write a script that puts an encoded string on the bottom of receipts. This string is what a customer would use to log on to a website and fill out a survey about the business.
So in this string, I would like to get a three-digit hard-coded location identifier, the date, and time; e.g.:
0010912041421
Where 001 is the location identifier, 09 the year, 12 the month, and 04 the day, and 1421 the military time ( 2:41 PM ). That way we know which location the respondent visited and when.
Obviously if we just printed that string, it would be easy for someone to crack the ‘code’ and fill out endless surveys at our expense, without having actually visited our stores. So if we could do a simple encryption, and decode it with a pre-set key, that would be great. The decoding would take place on the website.
The encrypted string should also be about the same number of characters, to lessen the chance of people mistyping a long arbitrary string.
What I want to use is XOR. It’s simple enough that we can do it in the proprietary scripting language ( we’re not going to be able to do any real encryption in it ), and if someone breaks it, they we can change the key easily enough.